The present invention relates to a single-substrate-processing CVD (Chemical Vapor Deposition) apparatus and method, and particularly to an apparatus and method for growing an insulating, high-dielectric, or ferroelectric film by means of MOCVD (Metal Organic Chemical Vapor Deposition).
In order to manufacture semiconductor devices, film formation and pattern etching are repeatedly applied to a semiconductor wafer. As semiconductor devices are increasingly highly miniaturized and integrated, demands on the film formation become more strict. For example, very thin insulating films, such as capacitor insulating films and gate insulating films are still required to be thinner and to be more insulating.
Conventionally, silicon oxide films and silicon nitride films are used as the insulating films. In recent years, however, it has been proposed to form the insulating films from materials having more excellent insulating properties, such as metal oxides, e.g., tantalum oxide (Ta.sub.2 O.sub.5), or high-dielectric or ferroelectric bodies containing two metal elements or more, e.g., (Ba,Sr)TiO.sub.3, i.e., BST. These films can be formed by means of MOCVD, i.e., using vaporized metal organic compounds.
When a film is formed by means of CVD, it is important to maintain a high planar uniformity in the film thickness, in light of attaining a high yield and the like. For this reason, process gases are supplied from gas spouting holes arranged at uniformly distributed positions on a shower head, so that the process gases are uniformly supplied onto the surface of a wafer. Where a CVD process is performed to form a film of a two-element material including only one metal or semiconductor element, represented by SiO.sub.2 or TiN, it is possible to maintain a high planar uniformity in the film thickness by such a shower head.
According to experiments conducted by the present inventors, however, where a CVD process is performed to form a film of a composite material including two metal elements or more, such as a BST thin film, planer uniformity in the film composition is sometimes lowered by this conventional CVD process. Like planar uniformity in the film thickness, planar uniformity in the film composition, i.e., the ratio of metal elements, is also an important issue, in light of attaining a high yield and maintaining electric properties.
Further, where a tantalum oxide film is formed by means of MOCVD, a raw material gas containing tantalum alkoxide, and oxygen gas are used. In this case, reaction byproducts, such as organic substances, e.g., CH.sub.3 CHO, are slightly mixed into the tantalum oxide film, thereby deteriorating the film's properties, such as the insulation breakdown voltage.